Generator-voltage regulator



3 Sheets-Sheet C. P. WEST GENERATOR VOLTAGE REGULATOR Fly: 1.

Filed Dec. 9, 1927 LL 8 e W Y R. M m R W m vm T m? A a h C B llll f m Wa fiqfi April 30, 1929.

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April 30, 1929.

c. P. WEST 1,710,755

GENERATOR VOLTAGE REGULATOR Filed Dec. 9, 1927 5 Sheets-Sheet 2 INVENTORCharles P. West April 30, 1929. R WE T 1,710,755

I GENERATOR VOLTAGE REGULATOR Filed Dec. 9, 1927 3 Sheets-Sheet 3 IA'l'l'A l 2 INVENTOR Charles P, West A ORNEY Patented Apr. 30, 1929.

- UNITED STATES V 1,110,155 PATENT OFFICE.

CHARLES P. WEST, OF PI'J.".I.SIBURGH, PENNSYLVANIA, ASSIGNOB '10WESTINGHOUSI ELECTRIC 8c MANUFACTURING COMPANY, A CORPORATION OFPENNSYLVANIA.

GENERATOR-VOLTAGE REGULATOR.

Application 'filed December 9, 1927. Serial No. 238,812.

This invention relates to a regulator for generators, the general objectof which is to maintain the generator voltage substantially constantunder all conditions of load.

Another objectof this invention is to provide a generator-voltageregulator which has no moving elements or contacts.

A further object of my invention is to provide a generator-voltageregulator by which any degree of overor under-compounding may beobtained.

A still further object of this invention is to provide agenerator-voltage regulator which shall not be subject to hunting orover-shooting.

Another object of my invention is to provide a generator-voltageregulator which is characterized by a quick response to changes in thegenerator voltage.

Another object of my invention is to arrange for the direct control ofthe generator field current.

Another object of my invention is to provide a method of regulation inwhich the corrective eii'ect is a function of line voltage, linecurrent, and load power-factor, co-ordinating the C01 rect act-ion ofeach to derive a net result which will compensate for each of the abovevariables under all conditions.

My invention may be more thoroughly understood by reference to theaccompanying drawings, in the various figures of which I haveillustrated several modifications of the invention.

Figure 1 is a diagram showing how my invention may be applied to adirect-current generator.

Fig. 2 is a diagram showing how the same system may be utilized inconnection with an alternating-current generator.

- Fig. 3 is a diagram of a slightly difierent I modification of myinvention shown in connection with an alternating-current genorator.

Fig. 4 is a graph illustrating the currentvoltage characteristics ofsome of the elements of the system shown in Fig. 3.

Fig. 5 is a diagram of a still further modification of my invention.

Fig. 6 is a graph similar to that shown in Fig. 4. I

Figs. 7 8 and 9 are vector diagrams illustrating graphically theoperation of the means which provide in the system of Fig. 5, forcompensating for variations in the power factor of the load supplied bythe generator.

Figs. 10 and 11 are diagrams illustrating further modifications of thesystems shown in Figs. 1 and 2.

In Fig. 1, is illustrated, at 1, a direct-current generator driven by aprime mover 2 which may be of any suitable type. The generator 1supplies current to the busses 3 and 4. At 5 is shown a three-leggedreactor hav- 65 ing a winding 6 equally distributed on the two halves ofthe core. The winding 6 is energized from a constant-potentialalternatingcurrent source 7 through a regulatin impedance 8, and isconnected to a rectifier 10 which may be of any suitable character, butwhich I have illustrated as of the copperoxide-disk type such asdisclosed in United States Patent 1,640,335, issued August 23, 1927, toL. O. Grondahl. The output of the rectified is supplied to the fieldwinding 11 of the generator 1 in series with which is connected awinding 12 on the center leg of reactor 5. Additional windings 14 and 15are placed on the center leg of the reactor core and are connected,respectively, across the busses 3 and 4, and to a shunt 16 in bus 4. Thewindings 14 and 15 are thus energized in accordance with the voltage of,and the load on the generator 1.

The embodiment of my invention shown in Fig. 1, in common with the othermodifications thereof shown in the remaining figures, depends, for itsoperation, upon the principle that the superposition of auni-directional flux upon an alternating flux in a magnetic circuit, hasthe effect of reducing the effective reactance of the winding inducingthe alternating flux. The winding 6 on the reactor 5 when energized bythe alternating-current source 7, induces an alternating flux whichconfines itself to the outer legs of the reactor core because of thefact that the primary winding is equally distributed on the two halvesof the core and, as a result, the net alternating flux in the center legis zero. Norreally, the winding 6 has a high reactanee. By means ofthewindings 11, 14 and 15, however, I arrange to superpose upon thealternating flux in the core of reactor 5, a unidirectional flux which,as explained above, has the effect of reducing the effective reactanceof the winding 6.

The manner in which the system shown in Fig. 1 operates to control thevoltage of the generator 1 will now be described. Assuming that thegenerator 1 is stationary, because of the high impedance of reactor 5,only a small current will flow from the alternatingcurrent source 7through the rectifier 10, resulting in a correspondingly small flow ofdirect current through the field winding 11 and thedirect-currentreactor winding 12. Now if the generator 1 is started,voltage will appear across the busses 3 and 1. This causes thecnergization of the winding 11 which, as shown by the arrows, is sowound that its magnetomotive force opposes that of the winding 12. Thewindings 12 and 1-1, however, are so designed that, during the period inwhich the generator voltage is building up, the winding 12 is moreeffective in saturating the reactor core than the windingl i. Theincrease in the net, uni-directional flux in the center leg of the core,resulting from energization of the winding H, reduces the reactance ofthe winding (3 in accordance with the explanation given above. Thereduction in the reactance of the winding 6 increases the currentsupplied to the rectifier 10 by the source 7, and it is for this reasonthat the field current builds up from its initial minimum to its normalvalue.

The winding 14, in cooperation with the winding 12, causes the generatorfield current to build up to the point at which normal excitation isprovided for the generator. Now, if the line voltage increases, becauseof a sudden decrease in load, for example, there will result an increasein the current in the winding 14. This, in turn, causes the reactance ofthe winding 6 to be increased because of the decrease in the net,uni-directional saturating flux, and, as a consequence, the generatorfield current is reduced to cause a reduction in the voltage acrossbusses 3 and 4.

If the line voltage decreases for any rea son, such as a suddenapplication of load, the first result will be a decrease in the currentthrough the winding 14. The next effect will be an increase in the net,uni-directional, saturating flux, causing a decrease in the reactance ofthe winding 6 followed by an increase in the output of the rectifier 10which increases the excitation of the generator to bring the generatorvoltage back to its normal value.

By utilizing an additional winding 15, it is possible to provide foroveror under-compounding of the generator 1. This is accomplished byenergizing the winding 15 in proportion to the current supplied to theload. If the winding 15 is so connected that its -magnetomotive forceaids that of Winding 12, the result will be that, as the load currentsupplied by the generator increases, the reactance of the Windingffl isdecreased, because of the increased uni-directional flux which saturatesthe transformer core, and the generator field current will be increased,

tending to increase the voltage generated, giving the generator thecharacteristic of a cumulative compound machine. If, however, thewinding 15 is so connected that its magnetic ctt'cct is opposed to thatof the winding 12, an increase in generator current will result in anincrease in the rsactance of the winding (3, because of the reduction ofthe uni-directional flux in the transformer core. This, obviously, willresult in a decrease in the generator field current and a decrease inthe generator voltage, and the generator will have a characteristicsimilar to that of a differential compound machine. The degree of overorunder-compounding may be controlled, of course, by suitablyproportioning the winding 15 and the shunt 16.

Fig. 2 illustrates a modification of my invention in which the generalscheme is the same as that shown in Fig. 1, the principal differencebeing that Fig. 2 illustrates an alternating-current generator 1, thearmature of which is connected to busses 17, 18 and 19. The reactor 5and its associated windings are identical with those shown in Fig. 1,except that the winding 6 may be energized from one phase of thegenerator. A separate alternating-current source, however, may beemployed, if desirable. The windings 14 and 15 are energized by directcurrent from rectifiers 20 and 21, in accordance with phase voltage ofthe generator and the load current, respectively, the rectifier 21 beingenergized by the current transforn'ier 22, in proportion to the loadcurrent.

The operation of the system shown in Fig. 2 is substantially the same asthat described in Fig. 1. The reactance of the winding (3 is varied inaccordance with the cnergization of the direct-currcnt windings 11, 14and 15 which are energized in proportion to the generator field current,generator voltage and the load current. The energization of the fieldwinding 11 is, of course, dependent upon the reactance of the winding 6,which controls the current supplied to the rectifier, and. in this way,the generator field current is varied in agreement with Variations inthe generator voltage and generator current to compensate therefor, asdesired.

In Fig. 3, is illustrated an improved system embodying my invention. Asin the previous figures, the generator 1 is driven by the prime mover 2and supplies current to a load connected to the busses 17, 18 and 19. Inthe system of Fig. 3, a constant-current transformer 30 is employed asthe source of alternating current for the device which I utilize tocontrol the generator field cur-. rent. The transformer 30 may beconnected to one of the phasesof the generator or may be supplied withalternating current from any suitable source. Connected in series withthe secondary of the constant-current transformer 30 are rectifiers 31and 32. The rectiltlll fier 31 supplies direct current. to the fieldtransformer will be energized from the winding of a reactor 36 having aniron core. The reactor 36 serves the same purpose as the reactors ot'the preceding figures. The current output of the transformer 3t) issubstantially constant be fause of its design characteristics, and, byvarying the eitective reactance of thereactor connected in parallel withthe rectifier 31, the current through the reactor may be varied,resulting in corresponding variations in the current supplied to therectifier 31 and to the field winding of the exciter 34. The ctlectivereactance of the reactor is varied by energizing direct-current windingson the center leg of the reactor 36.

The rectifier 32 supplies direct current to a winding 41 on the reactorfor the purpose ot'exciting the core witha uni-directional, biasingflux. The exciter 34 suppliesdirect current to the field winding of thegenerator 1 through the slip rings 37. In series with the generatorfield winding is connected the winding 39 on the reactor core. A winding38 is energized by'current from a rectifier 42 which is supplied withalternating cur rent from a current transformer 43- in accordance-withthe current supplied by the generator 1' to its load. The direetionsotthe magnetoinotive forces of the various windings on the center leg ofthe reactor core.

are indicated by arrows.

A voltage-compensating winding is connected to a local circuitcomprising rectifiers 44 and 45' in series and two equal resistors 43and 49, at points between the rectitiers and the resistors. Therectifiers 44 and 45 are connected to the secondaries of transformers 46and 47, the primary windings of which are connected in series with areactor 50 and a resistor 51, respectively. The reactor and the resistorcircuits are connected, in parallel. to one phase of the generator andhave characteristics such that, when normal generator voltage existsacross the conductors 13 and 19, equal currents will flow through thereactor. and the resistor. Under these conditions, the direct-currentvoltages of the rectifiers 44 and 45 will be'equal. and the voltage at apoint between the r'ectifiers will be the same as that of a pointbetween the resistors 43 and 49. Consequently, there will be no currentflowing through the winding 40. The characteristics of the reacto 5t)and the resistor 51 are shown inFig. 4 by the curve and the straightline, respectively.

The operation of the regulating system shown in Fig. 3 may be describedas 't'ollows:

Consider that the generator 1' is being driven at normal speed by theprime mover 2 and is,v generating normal voltage. The

generator 1, and the rectifier 31 will supply current to the field ofthe exciter 34. The rectifier 32 supplies direct-current to the winding41 to bias the core of reactor 36, so as to reducethe etl'ective valueof the reactance of the winding 35, to control the current supplied tothe exciter field by therectiticr 31. The winding 32) is in series withthe field of the generator 1, and its magnetomotive force opposes thatof the winding 41. The magnetolnotivc force of the winding 33 alsoopposes that of the biasing winding 41, and that of the winding 40 maybe in either direction, depending upon the direction ot'current in thewinding. 3

Under normal operating conditions, the constants of the circuit aredesigned so that normal current will flow through the field winding ofthe exciter 34. It the bus voltage should, for any reason, such as asudden removal of load. be increased above its nornial value. thecurrent through the resistor 51' will'be greater thanthat through thereactor 50. as may be observed from curves shown in Fig. 4. This willresult in an unbalanced condition in the local circuit including therectifiers 44 and 45 and the resistors 43 and 49. Direct current willthen flow in the winding 40 in such direction as to aid.

the winding 41 in saturating core 34. This r sults in adecrease in theeffective value of the reactance ot the winding 35 and a decrease in thecurrent supplied by the transformer 30 to the rectifier 31. The currentsupplied to the field 33 of the exciter 34 is.

in turn. decreased, and the current supplied to the field winding ofgenerator 1 is correspondingly decreasedto reduce the gen eratedvoltage.

If, however, the bus voltage should decrease for any rcason,thedirect-current voltages of the rectifiers 1-4 and 45 would be unequal,and the local circuit, including the l'octilicrs 44 and 45 and theresistors 48 and 45). would again be unbalanced but the current suppliedto the winding 40 in this case would be in such direction as to opposethe saturating niagnetoniotive force of the winding 41, and to increasethe reactance of the winding 35 which, of course, causes a greaterportion of the output of transformer 30 to pass through the rectifier31, resulting in an increase in the exciter field current which resultsin-an increase in the generator voltage. The winding38is soconncctcdthat the directcurrent supplied to it from rectifier 42 sets up amagnctoulot'ivo force opposing that of the saturating winding 41. inproportion to the current supplied by'the generator 1 to its load. Ifthe generator current increases, the inagnetomotive force of the winding38 opposes that ofthe winding 41. decreases the saturation of the core34 and increases the eftective'value of the reactance of the winding 33so that more current is supplied by the rectifier 31 to the field 35 ofthe exciter 36. In this manner, an increase in generator load "currentis followed by an increase in generain opposition to that of the winding41. As a result of' this arrangement, any change in the system whichtends to increase the generator field current, by means of the winding39, tends to increase the reactance of the winding 33 and thereby toincrease the exciter field current, to still further increase thegenerator field current. The same is true of any invfiuence tending todecrease the generator field current.

By suitably designing the elements of the system illustrated in Fig. 3,it may be possible to eliminate the exciter 34 and to utilize therectifier 31 to supply direct currentdirectly to the field winding ofthe generator 1'. By the use of such a system, even quicker response tochanges in the load circuit is obtained.

It is to be noticed, in connection with the system shown in Fig. 3, thatno moving parts are employed and no contacts are required to be made orbroken. There is no tendency for this regulating system to hunt orovershoot. This is because of the fact that the corrective effect or, inother words, the influence tending to bring the generator voltage backto normal, in case of variation therefrom. is proportional to thevariation from normal voltage. As a result of these characteristics,when the generator voltage approaches its normal value, the tendency forit to be corrected to that value is'correspondingly decreased. In thecase of a wide divergence of the generator voltage from its normalvalue, .a correspondingly strong tendency will be effective to bring thevoltage back to normal. These characteristics represent markedadvantages over voltage regulators known heretofore.

Fig. 5 illustrates the circuit diagram of a further modification of myinvention which is an improvement over that described above. In thismodification, I provide not only for compensating for load current andgenerator voltage, but also for load power factor.

The alternating-current generator is indicated at 1 and its associatedprime mover at 2. Direct current for the generator field is controlledby a rheostat 52 and is obtained from rectifiers 75 which areillustrated as of the mercury-arc type and which are energized by thetransformers 76, the primaries of which are connected to the basses 1718 and 19. In series with the primary windings of the transformers 76,are the exciting windings 77 of the reactors 78, 79 and 80. The" by thetransformer 87 in accordance with the load current supplied by thegenerator 1,

The winding 82 is energized by current from a local circuit includingthe rectifiers 88, 89 and the resistors 90 and 91, in exactly the samemanner as described in connection with Fig. 3, the rectifiers 88 and 89being in series with imp'edan'ces 92 and 93 of differentcharacteristics, as shown in Fig. 6, such that, at normal generatorvoltage, equal currents flow through the said impedances. The im-'pedances 92 and 93 are supplied with current from the tertiary'wiudmg ofa transformer 94 connected to one of the generator phases. The winding83 is energized by the output of rectifier 95 which also is connected tothe tertiary winding of transformer 94. The function of the winding 83is to supply a constant, uni-directional, biasing flux in the core ofthe reactor.

The windings 84 and 85 are energized by direct current from rectifiers96 and 97, respectively. Alternating current is supplied to'theserectifiers by means of current transformers 100 and 101, respectivelyand also by the secondary winding of transformer 94 which suppliescurrent to a condenser 98 and an inductance 99, in parallel, which areconnected to the rectifiers 96 and 97, respectively.

It is well known that a synchronous alternating-current generatorrequires less excitation for the same output at a leading power factorthan at a lagging power factor, and it is the function of the windings84 and 85 to control generator field current in accordance with thepower factor of the load current. The manner in which this isaccomplished may be best understood by considering Figs. 7, 8 and 9, inconnection with Fig. 5.

The current transformers 100 and 101 supply the rectifiers 96 and 97with an alternating current proportional to, and in phase with thecurrent supplied by the generator to its load. The transformer 94,through the condenser 98 and the inductance 99, supplies to therectilfiers 96 and 97, respectively, currents which are in leading andlagging quadrature, respectively, with the generator voltage. Theenergization of the windings 84 and 85 of the reactor 78 is a functionof the resultants of the leading and lagging quadrature components ofthe current from the condenser iao E represents the generator voltageand I represents the enerator current. In leading quadrature with thegenerator voltage is the current 1 and, in lagging quadrature with thesame voltage, is the current I These currents are obtained from thecondenser 98 and the inductance 99. The resultant of I and I isindicated at 1,, while the resultant of I and I is shown at I Thecurrents I and I respectively energize the rectifiers 97 and 96, and thewindings 85 and 84 are energized by direct current from the rectifiersin the same proportion. The windings 84 and 85 are connected sothat'their magnetoinotlve forces are opposing. When the power factor ofthe load is unity, therefore, the magnetic efiect of the two windings isequal and opposite, and the net effect is zero; v

In Fig. 8, the condition of lagging power factor of the load current isillustrated. In

this case, the leading quadrature component I combined with the loadcurrent I, results in the current I and, similarly, 1,, is the resultantof I andI. It is obvious that, at lagging power factor, I is larger thanI and, as a result, the'winding 85 energ1zed thereby will exert agreater effect on the magnetic circuit of reactor 78 than the winding 84energized by I The inagnctomotive force of the windin g 85 is insuchdirection as to aid that of the saturating winding 83. As a result oflagging power factorof the load current, the winding 85 exerts astronger effect on the magnetic circuit than the winding 84 and, aidedby the effect of winding 83, saturates the core 78 to decrease thereactance of the Winding 77, permitting more current to flow through theassociated primary of the transformef76 connected thereto, so that agreater field current is supplied to the generator field from theassociated rectifier 75.

When the power factor of the load is leading, however, conditions are asillustrated in Fig. 9. In this case, the resultant I is greater than 1,,and, consequently, the wind- .ing 84 of the reactor 78 is more effectivein saturating the core than the opposing wind- .ing 85. The efiectof'the winding 84 is to decrease the saturation of the core, as a whole,and to increase the reactance of the winding 77 which, in turn,decreases the current in the primary of the transformer 76 and alsodecreases the output of the rectifier 75, decreasing the generator fieldcurrent to reduce the excitation. In this manner, the system of myinvention operates so to vary the excitation as to compensate for anychange in power factor of the load current.

Although, for the sake of clearness, I have shown thepower-factor-compensating means only on the reactor 78, it is, ofcourse, obvious that the'same compensation should be applied to thewindings 84 and 85of the reactors 7 9 and 80. The saturating winding 83is also employed on the reactors 78 and 79.

winding (5 connected in parallel.

The voltage-compensation means shown in connection with reactor 80 1s,of course, applied also to the wmdmg 82 of reactors 78 and 7 9. Eachphase of the generator is thereby provided with means for compensatingfor all variables, VIZ, voltage, current and power factor.

Fig. 10 illustrates a still further modification of my generator-voltageregulator which is similar to that shown in Fig. 1. In Fig. 10, however,the rectifier, supplying the direct current to the generator field, isconnected in parallel with the reactor which controls the value of thegenerator field current. In Fig. 10, the generator is shown at 1, theprime mover at 2 and the reactor at 5. The winding 6 of the reactor 5 isenergized by an alternating-current source 7 through an impedance 8, thevalue of which, in comparison to that of the reactor, is sufiicentlyhigh so that a substantially constant current is supplied by the source7. Any other constant current source, however, may be substituted forgenerator 7 and impedance 8. In addition to the windings 12, 14 and 15,shown in Fig. 1, I provide an additional winding 13 on the center leg ofthe reactor 5 which is supplied with direct current from rectifier 10,which is in series with the recti tier 10 and the The function of thewinding 18 is to saturate the core of the reactor 5 with a substantiallyconstant flux, to reduce the impedance thereof so that only a smallcurrent is supplied to the field 11 by the rectifier 10, when thegenerator is stationary.

\Vhcn the generator is started, however, the small current supplied tothe field thereof causes a small voltage to be generated and thisvoltage energizes the winding 14 which is connected to the busses 3 and4. The magnet- ()ll'lOtlVO force of the winding 14, as shown by thearrows, is in the same direction as that of winding 13. The winding 12is in series with the generator field winding and the rectifier 10 andis so connected that its magnetic effect is opposed to that of winding14. These windings are so designed that winding 12 is more eitective insaturating the core than winding 14, during the period in which thegenerator voltage is building up. As the voltage on the busses 3 and 4increases, the saturating liux in the core of the reactor 5 is reducedbecause of the increased energization of windings 12 and 14, and theimpedance of the reactor is therefore increased. This results in alarger current through the rectifier 10 and, of course, a largerdirectcurrent output therefrom to the generator field. 11.

The winding 12, as in Fig. l, is energized by the current supplied tothe generator field, and its action is to hasten any change in thegenerator field current resulting from a change in generator voltage.The function of the winding 15, which is energized in pro portion to thecurrent supplied by the generator l to its load, is the same as that ofthe corresponding winding in Fig. 1.

If the bus volta e rises, because of a sudden removal of load,forinstance, the current in winding 14 is increased, and, therefore thenet saturating flux is increased. 'The reactance of winding 6 issimultaneously reduced, and the current supplied to the generator field11 is decreased. I

If the bus voltage decreases, however, when load is suddenly applied tothe generator, the.

decrease in the current through winding 14 increases the impedance ofreactor 5 by decreasing the saturating flux, and a greater current isthereupon supplied to the generator field winding 11by rectifier 10.

Fi 11 illustrates a system similar to that of Fig. 10 except that it isdesignedfor use Some of the obvious advantages of the sys ternsdescribed above are as follows:

No moving parts or contacts are utilized.

This method of regulating permits the controlling of the generator fielditself whereas, in regulating devices heretofore known, the exciterfield only, is subject to the control of the regulating evice. Theregulator of my invention is, of course, very much quicker to res 0nd tovoltage variations than those in which the exciter field current isaltered to control the generator voltage.

There is no tendency toward huntingl, sincethe corrective forcedecreases as the voltage approaches its normal value.

No rotating exciter is required and the delay introduced thereby isavoided.

By my method, the generator field current is made a function of thegenerator voltage, generator current and load power factor, eachco-ordinating to produce a net result Y which compensates for each ofthe variables under all conditions.

I claim as my invention:

1. A regulator for controlling the voltage of a generator comprising areactor having a winding connected to an alternating-current source, arectifier for supplying direct current to the field windings of saidgenerator connected in series with said reactor winding, said reactorhaving also direct-current windings energized in accordance with thegenerator voltage and load current, respectively, tending to vary theenergization r of said field windings in response to variatio'ns in thegenerator voltage and load current.

2. A regulator for. controlling the voltage of a generator comprising areactor energized from an alternating-current source, direct-currentwindingson said reactor for controlling the effective reactance thereof,said direct-current windings being energized, respectively, inproportion to the generator voltage, load current and field current, anda rectifier connected in series with said reactor for supplying directcurrent to the field winding of said generator in accordance with thecurrent-and voltage out-' put of the generator.

3. A regulator for controlling the voltage of a generator comprisingmeans for energizing the field of the generator exciter from thegenerator, an impedance in parallel with said means and means forvarying the effective value of said impedance in proportion to thegenerator output so as to vary the current supplied to the exciter fieldwhereby the generator voltage is maintained substantially constant underall conditions. i

4. In a regulator system .for controlling the voltage of analternating-current generator, an exciter for said generator, aconstand-current transformer connected to the generator, a rectifier andan impedance in parallel, energized by said transformer, said rectifierbeing connected to supply direct current to the field winding of thegenerator exciter, and means for varying the effective value of saidimpedance in proportion to the generator output to vary the currentsupplied to said exciter field, whereby .the generator voltage ismaintained substantially constant. a

5. A regulator'system for controlling the voltage of analternating-current generator comprising an exciter for said generator,a constant-current transformer connected to the generator, a rectifierand an iron-core reactor in parallel, energized by said transformer,said rectifier being connected to supply direct current to the fieldwinding of the generator exciter, direct-current saturating windings onsaid reactor for varying the effective value thereof in accordance withthe generator output to vary the current supplied to the exciter field,whereby the generator voltage is maintained substantially constant underall conditions of load.

6. A regulator for controlling the volta e of an alternating-currentgenerator compr1s ing an exciter for the generator, a constantcurrenttransformer connected to the generator,'a rectifier and an iron-corereactor in parallel, energized by said transformer, said rectifier beingconnected to supply direct current to the field winding of the-generatorexciter, direct-current windings on said reactor, energized throughtransformers and rectifiers in accordance with the generator from saidsourcedsaid rectifier supplying direct current to the field of thegenerator exciter, whereby the excitation of said exciter may becontrolled by varying the cfiective value of saidreactance.

8. In a regulating system for controlling the voltage of a generator, anexciter for the field winding of said generator, a constantcurrenttransformer, a rectifier connected to said transformer for supplyingdirect current to the exciter field winding, and a variablc'reactorinparallel with said rectifier for controlling the current supplied tosaid exciter field in accordance with the output of said generator. l

9. A regulating system for maintaining the voltage of ana'lternating-current generator substantially constant comprising aconstant-current transformer connected to the generator, a rectifier andan iron-core reactor connected in parallel to said transformer, saidrectifier being a'dapted to supply direct current to the field windingof the generator exciter, means for varying the effective value of saidreactor in accordance with changes in generator voltage, to vary theexcitation ofsaid exciter correspondingly, said means including a directeurrent winding on said reactor, the current in which is altered inaccordance with the generator voltage, whereby the generator voltage ismaintained substantially constant.

10. The method of varying the direct current supplied to the fieldwinding of a generator exciter by a rectifier connected to a source 1 ofconstant alternating current in parallel with a reactor which consistsin varying the effective value of said reactor.

11. The method of varying the direct current supplied to the field of agenerator exciter bv a rectifier connected to a source of constantalternating current in parallel wlth 'proportion to the voltage of thegenerator.

12. The method of.controlling the excitation of a generator having anexciter, the

field of which is energized by a rectifier connected to a source ofconstant alternating current in parallel with an iron-core reactor whichconsists in superposing on the alternating flux in the core of saidreactor a con 'stant unidirectional flux and an opposing unidirectionalflux and varying the latter flux in proportion to the current andvoltage supplied y the generator and to the generator field current.

13. The combination with a generator regulator comprising a source ofconstant alternating current, a rectifier, a reactor connected inparallel therewith to said source of constant alternating current, saidreactor'having a direct-current winding on itscore to vary its effectivevalue, of means for compensating for Variations in generator voltagecomprising impedances having volt-ampere characteristics which intersectat normal generator voltage, connected in parallel to the generator,rectifiers for rectifying the current through said impedances, thedirect-current terminals of said rectifiers being connected in series ina local circuit, said direct-current winding befor supplying directcurrent to thegenerator field from the. generator output, an impedancein series withsaid means and means for varyin g said impedance, to varythe field current, in accordance with the generator voltage; thegenerator current and the power factor of the load. 16. A system forcontrolling the voltage of an alternating-current generator comprisingmeans for supplying direct current to the generator field from thegenerator output, an iron-core reactor in series with said means, andmeans for varying the effective value of said reactor, to vary the fieldcurrent, in accordance with the generator voltage, the generator currentand the power factor of the load.

17. A static regulator for .generators comprising an iron-core reactorfor Controlling the generator field current, direct-current windings onsaid reactor for varying the efiec tive value thereof in accordance withthe generator voltage, the generator current and the power factor of theload.

18. A static regulator for alternating-current generators comprisingrectifiers for supplying direct current to the generator field from thegenerator output, the rectifiers being connected to the generator, aniron-core reactor in series witheach of said rectifiers, for controllingthe generator field current, direct-current windings on the cores ofsaid reactors for varying the effective value thereof, and additionaltransformers and reeti'fiers forenergizing said direct-current windingsin accordance with the generator voltage, the generator current and thepower factor of the load.

19. In a system for controlling the voltage of an alternating-currentgenerator, an ironcore reactor for controlling the generator fieldcurrent, a direct-current winding on one core of said reactor forvarying the effective Value thereof, a rectifier and a currenttransformer having its primary connected in a generator lead and itssecondary to said rectifier for energizing said direct-current windingin proportion to the generator current. I

20. In a system for controlling the voltage of an alternating-currentgenerator, an ironcore reactor for controlling the generator fieldcurrent, opposing direct-current windthe effective value of the latterand power factor compensating means for energizing one of said windingsin proportion to the resultant of the generator current and a current inleading quadrature with the generator voltage, and the other winding inproportion to the resultant of the load current and a current in laggingquadrature with the generator voltage. x

21. In a voltage regulator for generators, the combination of aniron-core reactor for controlling the generator field current. havingopposing direct-current windings for varying its effective value, withpower factor compens. ting means comprising means for obtaming currentsin leading and lagging quadrature with the generator voltage, means forvectorially combining these currents with the generator current, andmeans for energizing said opposing windings with direct currentproportional to the resultants of the generator current and the leadingand lagging quadrature currents, respectively.

22. In a voltage regulator for generators, the combination of aniron-core reactor for controlling the generator field current, havingopposing direct-current windings for varying the efieetivevaluethereof,with power factor compensating means comprising a condenserand an inductance connected in parallel to the generator, currenttransformers also connected to the generator, said coudens er and one ofsaid transformers being connected to a rectifier sup-plying one of saiddirect-current windings, the inductance and the other transformer beingconnected to a ings on the core of said reactor for changing secondrectifier supplying the other directcurrent winding, whereby thegenerator field current is increased when the power factor is lagging,and decreased when it is leadin In a. generator voltage regulator, thecombination of an iron-core reactor for controlling the generator fieldcurrent and having a direct-current winding for varying the effectivevalue thereof, with voltage compensating means comprising impedanceshaving diil'erent voltage current characteristics, which intersect atnormal generator voltage,

connected in parallel to the generator, a local circuit, means forrectifying the currents through said impedances and supplying them tosaid local circuit, said direct-current winding being connected to saidlocal circuit at points which are of equal potential when the currentsthrough said impedances are equal.

24. In a voltage regulator comprising an iron-core reactor forcontrolling generator field current and having opposing direct-currentwindings thereon for varying the effective reacta-nce thereof, themethod of compensating for variation in the power factor of the loadwhich consists in energizing one of said windings in proportion to theresultant of the load current and a current in leading quadrature withthe generator voltage, and energizing the other direct-current windmg inproportion to the resultant of the load current and a current in laggingquadrature with the voltage.

25. In a voltage regulator comprising an iron-core reactor forcontrolling generator field current and having a direct-current windingthereon for varying the effective value thereof, the method ofcompensating for var ations in generator voltage which consists 1nenergizing said winding with current in one direction if the generatorvoltage is high and in the other direction if it is low.

26. In a voltage regulator comprising an iron-core reactor forcontrolling generator field current and having a direct-current windingthereon for varying the effective value thereof, the method ofcompensating for variations in generator voltage which comprisesaltering the direction of the direct current in said winding inaccordance with the value of the generator voltage.

In testimony whereof, I have hereunto subscribed my name this 5th day ofDecember,

CHARLES I. IVEST.

